Harvesting densely planted, tall, stalky plants, including, but not limited to, sweet sorghum, for biomass and energy has long been known. Commonly, conventional harvesters have been used for harvesting sorghum, including grain, forage, and sugarcane type harvesters, each having advantages and disadvantages. With sorghum, sugars contained in the stalks is a sought after element of the plant. However, it has been found that an undesirable amount of the juices containing the sugars can be lost or the juices undesirably degraded if the stalks are chopped into small bits and stored in that state prior to the extraction process. It has also been found that sorghum stored in small chipped form can generate undesired levels of heat when stored. It is therefore desired to harvest sorghum in a manner that preserves more of the juices in the harvested plant. A challenge of harvesting sorghum is that the harvesting season can be many months long per year and any harvester used should be designed for a relatively high annual duty cycle. Another challenge is that sorghum is sometimes relatively densely planted compared to similar tall plants such as sugarcane, and use of a conventionally configured sugarcane harvester for harvesting sorghum can be slower than desired.
Examining the various types of harvesters used for sorghum, known grain type harvesters are advantageous as they allow harvesting wide swaths of crop in a row insensitive manner, that is, at any location across a width of a header of the combine, without need for alignment with the rows of plants being harvested, and can rapidly process the resulting large mass of harvested crop material. Grain harvesters can also collect the grain separately of stalks and other crop residue. Disadvantages include that grain harvesters typically are constructed to operate on relatively small annual duty cycles, and are not known to have a suitable manner of preserving juices in the harvested stalks. Crop material flow through a typical grain harvester additionally is in the form of a non-sequential mixture of crop material, including stalks, leaves, grain, and other portions of the plant, wherein the stalks are not deliberately oriented in any particular direction. As a result, the stalks are not adequately aligned in a manner to facilitate cutting into billets of a particular length or range of lengths with desired uniformity.
Forage harvesters are advantageous as they can also harvest in a row insensitive manner, that is, cut crops at any and all locations across the width of a header of the harvester, and can induct a high volume mass of cut crop material from the header into the harvester. Forage harvesters also have a large capacity rotary cutter or chopper that can rapidly chip or cut the received crop material into small chips or particles, e.g., smaller than a kernel of maize or corn, suitable for conveying using pneumatic systems. Disadvantages of known forage type harvesters include that that they too have a relatively short annual duty cycle, and the chipping type rotary cutter is not adapted for cutting stalks in a manner to produce billets of a desired length found to best preserve juice, e.g., in a range of from about 100 to about 500 millimeters.
Sugarcane harvesters are advantageous as they have a relatively long duty cycle, and they billet the cane, including in the above stated range, if desired. Some sugarcane harvesters also have a capability to clean or remove leaves from the stalks in a variable manner so that the amount of remaining leaves on the stalks can be controlled, which may be desirable. However, cane harvesters are disadvantageous as they are row sensitive, that is, the apparatus or header for cutting and inducting the canes into the harvester requires alignment with a limited number of the rows of canes spaced a certain distance apart during movement over the field. This is required to enable processing of the cut canes in a sequential, end to end order wherein the plants are individually stood up, topped (removal of top foliage) and base cut (base of canes severed from ground at or near ground level), by the harvester as necessary for harvesting desired portions of the plants. For purposes of harvesting sweet sorghum and some other tall stalky plants for biomass or energy production, this degree of processing is unnecessary and would serve to increase harvesting time and decrease productivity. As another disadvantage, sugarcane cultivation is well known and the row spacings between sugarcane plants are presently uniform at either 1.4 meter or 1.8 meter, and in some limited instances narrower spacings, whereas row spacing for sweet sorghum and other plants to be used for energy production have not been standardized yet.
Reference Caillouet U.S. Pat. No. 6,062,009, issued May 16, 2000, which discloses a representative row sensitive apparatus and method for harvesting cane and cutting the cane into billets. The Caillouet apparatus is configured for topping, base cutting, inducting, cleaning, and billeting two rows of cane simultaneously. The Caillouet apparatus utilizes side by side chain gatherers for receiving and holding canes of each of the two rows in a generally vertical semi-erect orientation for topping and base cutting by a rotary base cutter located below the rear end of the gatherers, and a turn around device for moving the canes laterally and throwing the topped ends down away from the harvester, for induction into the harvester cut base end first, in sequential order for subsequent stripping and billeting. Stripping or cleaning apparatus is located in a middle area of the harvester and strips leaves from the canes as they transition from the base cutter to an inclined lifting conveyor that conveys the canes in end to end sequential order upwardly and rearwardly to a billet cutter. The billet cutter cuts or severs the canes sequentially as they are conveyed by and propelled from the end of the lifting conveyor to a further cleaning device, receiving container, or other location.
As a disadvantage, the Caillouet apparatus is not configured to cut canes or stalks in a row insensitive manner, nor is it contemplated to billet cut a large number of canes simultaneously. In this latter regard, although more of a limitation than a disadvantage, many known billet cutters utilize parallel rotating drums having knives running the length of the drum at angularly spaced locations about their circumference, respectively, the knives of the respective drums cooperating with the other drum for cutting canes or stalks captured between the drums to certain lengths. This requires the width of the gap between the drums to closely match the thickness or width of the canes or stalks to be cut, to ensure that the canes are completely cut through, and not allowed to pass through uncut or only partially cut.
It would be desirable to develop a harvesting system and method that provides the annual duty cycle and billet cutting capabilities of sugarcane harvesters, with a row insensitive plant cutting and gathering capability, suitable for harvesting tall, stalky plants such as sweet sorghum, cane, and the like, which overcomes one or more of the disadvantages and limitations set forth above.